Influence of hydraulic conditions over bed-forms on the distribution of the benthic macroinvertebrates in the Spree River (Germany).

BLETTLER, M.; SUKHODOLOV

Leibniz-Institute of Freshwater Ecology and Inland Fisheries Berlin, Germany (IGB).

Conferencia; IGB Serie of conferences; 2009

Leibniz-Institute of Freshwater Ecology and Inland Fisheries Berlin, Germany (IGB).

The research outlined in this study was designed to clarify the effects of highly dynamical hydro-morphological processes on ecology of invertebrates in lowland rivers. Specifically the focus is set on the aquatic bed-forms, ubiquitous element in fine graded alluvial channels, and their influence on benthic macroinvertebrate spatial distribution, bio-diversity of their communities. The study had explored the similarities in the processes governing the ecology of invertebrate communities across a wide range of scales by performing a comparative analysis of data collected in the relatively small lowland river Spree in Germany and in the large Middle Paraná River in Argentina. The principal research goal was to clarify the effects of hydro- morpho- dynamic processes on ecology of invertebrates in rivers. Specifically, the focus was set on a sequence riffle- transitional- pool zone of a meander and benthic macroinvertebrate spatial distribution, on bed-forms on the riffle zone of a meander and benthic distribution, and finally on the structure of flow prevailing over the stoss-side, crests and lee-side and its effect on benthic distribution.  The secondary research goal was also to clarify the scaling relationships comparing the Spree River results and previous similar data of the large Paraná River (Argentina). The results suggest that at meso-habitat scale (i.e. riffle, pool and transitional zone) the more intense hydraulic conditions are finding on the riffle zone, where considerably lower densities of invertebrates were recorded. At micro-habitat scales (i.e. within bed-form) the hydraulic conditions varied between the stoss-side, crests and lee-side. Specifically, the global hydraulic conditions were higher on lee-side. The highest benthic densities were found on the crest, where bed shear stresses are lowest (difference around 33%) and the lowest densities were recorded on the stoss-side and lee-side. Apparently, the organisms prefer the crest of the dune because of the benefit of low flow and a stable environment (which provide refuge and food).